Air conditioning apparatus

ABSTRACT

The air conditioning apparatus of the present invention includes a refrigeration cycle device formed by connecting an outdoor unit equipped with a compressor with a plurality of indoor units, the indoor unit performs an air conditioning operation by switching between an thermo-on operation for performing a cooling operation or a heating operation and a thermo-off operation for suspending the cooling operation or the heating operation by using information on temperature difference between a suction air temperature and a set temperature, and shifts to a start-stop suppression operation mode for making any indoor unit perform the thermo-on operation in a case where an indoor unit A has met a thermo-off condition for switching from the thermo-on operation to the thermos-off operation and in a case where there is none of the indoor units is in the thermo-on operation other than the indoor unit A.

TECHNICAL FIELD

The present invention relates to an air conditioning apparatus.

BACKGROUND ART

Conventionally, there has been known an air conditioning apparatus that is configured by connecting an outdoor unit equipped with a compressor with a plurality of indoor units and performs an air conditioning operation such that a suction air temperature of each indoor unit reaches a set temperature that is to be set for each indoor unit. Although as such an air conditioning apparatus, one is known that controls the capacity of the compressor conforming to an air conditioning load, when the air conditioning capability becomes excessive due to mismatching with the air conditioning load and so forth, it enters a start-stop state that operation and stop of the indoor unit are repeated.

Specifically, for example, at the time of cooling operation, when the suction air temperature in each indoor unit reaches a lower limit value that is determined in accordance with the set temperature, the corresponding indoor unit shifts from a thermo-on operation for performing the air conditioning operation to a thermo-off operation for stopping the air conditioning operation. Then, after the room temperature has been sufficiently increased by an indoor load, the indoor unit shifts again to the thermo-on operation and lowers the room temperature.

In such an air conditioning apparatus, in a case where all of the indoor units have entered the thermo-on operation, it is necessary to stop the compressor and therefore an increase in power consumption and reduction in operating efficiency associated with start-stop of the compressor occur.

For example, in Patent Literature 1, in particular, in a case where a plurality of the indoor units have been installed in a large space and in a case where the air conditioning loads of the respective indoor units coincide with one another, timings that the plurality of indoor units enter the thermo-off operation are liable to synchronize with one another. Regarding such a problem, in Patent Literature 1, a control unit performs indoor thermo-timing changing control for changing a thermo-temperature width of anyone of the plurality of indoor units, thereby positively producing an indoor unit that is different from other indoor units in timing that it is made indoor thermo-off and/or indoor thermo-on. It is stated that it can become easy to obtain a situation that at least one of the plurality of indoor units is operating by such control.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2012-154600

SUMMARY OF INVENTION Technical Problem

However, the abovementioned prior art has such a problem as follows. That is, although in a case where the loads of the plurality of indoor units coincide with one other, the synchronized timings can be deviated from one another, for example, by lowering the thermo-off temperature of one indoor unit, in a case where they are not fully synchronized with one another and in a case there exists an indoor unit that is different in cycle such as in a case it is installed in a different room, there is the possibility that a sufficient effect cannot be obtained.

In addition, since the air conditioning load is not fixed and fluctuates with time, even though the synchronized timings can be deviated from one another by lowering the thermo-off temperature, there is the possibility that they may be again synchronized with one another associated with load fluctuation. Nothing is considered with respect to such a problem and there is a problem in terms of certainty and practicability.

In addition, since an operation for deciding cyclicity of the indoor units and the outdoor unit is needed, there is such a problem that control cannot be started until after the operation has been continued for a predetermined time.

In addition, for example, in a cooling operation, since an operation that the thermo-off temperature of a certain indoor unit has been lowered will be continued, a room temperature in the vicinity of the indoor unit concerned will be lowered relative to the set temperature. Accordingly, it has such a problem that a cooling load is increased to increase the power consumption of the air conditioning device. Further, since an operation of low efficiency that an evaporating temperature has been lowered will be continuously performed due to this, while the energy saving effect can be obtained in a case where start-stop of the compressor can be avoided, there is the possibility that the power consumption may be increased conversely in a case where start-stop of the compressor occurs.

In this way, in the prior art, while there is the possibility that a start-stop frequency can be reduced, it had the problem from such a viewpoint that the power consumption is to be reduced.

The present invention proposes to provide an air conditioning apparatus that suppresses an increase in power consumption associated with start-stop of the compressor and is high in energy saving property.

Solution to Problem

In the air conditioning apparatus of the present invention including a refrigeration cycle device formed by connecting an outdoor unit equipped with a compressor with a plurality of indoor units, the indoor unit performs an air conditioning operation by switching between an thermo-on operation for performing a cooling operation or a heating operation and a thermo-off operation for suspending the cooling operation or the heating operation by using information on temperature difference between a suction air temperature and a set temperature, and shifts to a start-stop suppression operation mode for making any indoor unit perform the thermo-on operation in a case where an indoor unit A has met a thermo-off condition for switching from the thermo-on operation to the thermos-off operation and in a case where there is none of the indoor units is in the thermo-on operation other than the indoor unit A.

Advantageous Effects of Invention

According to the present invention, there can be provided an air conditioning machine that can reduce the start-stop frequency of the compressor so as to suppress an increase in power consumption associated with start-stop of the compressor and is high in energy saving property by appropriately changing the thermo-on/thermo-off conditions of the indoor unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration of an air conditioning apparatus of a first embodiment.

FIG. 2 is a diagram showing a relation among signals from a remote controller, a controller and each actuator.

FIG. 3 is a diagram showing an operational example in conventional control.

FIG. 4 is a diagram showing an operational example of the first embodiment.

FIG. 5 is a flowchart of the first embodiment.

FIG. 6 is a diagram showing an operational example at the time of heating operation.

FIG. 7 is a diagram showing an operational example that continuation of a start-stop suppression operation mode has been restricted depending on the temperature.

FIG. 8 is a diagram showing an operational example that continuation of the start-stop suppression operation mode has been restricted depending on the time.

FIG. 9 is a flowchart of a second embodiment.

FIG. 10 is a diagram showing an operational example of the second embodiment.

FIG. 11 is a diagram showing an operational example of a third embodiment.

FIG. 12 is a diagram showing an operational example of a fourth embodiment.

DESCRIPTION OF EMBODIMENTS

In the air conditioning apparatus of the present invention including the refrigeration cycle device formed by connecting the outdoor unit equipped with the compressor with the plurality of indoor units, the indoor unit performs the air conditioning operation by switching between the thermo-on operation for performing the cooling operation or the heating operation and the thermo-off operation for suspending the cooling operation or the heating operation by using information on temperature difference between the suction air temperature and the set temperature, and shifts to the start-stop suppression operation mode for making any indoor unit perform the thermo-on operation in a case where the indoor unit A has met the thermo-off condition for switching from the thermo-on operation to the thermos-off operation and in a case where there is none of the indoor units is in the thermo-on operation other than the indoor unit A. According to the present invention, owing to provision of the start-stop suppression operation mode for making any one of the indoor units perform the thermo-on operation in a case where the indoor unit A has met the thermo-off condition for switching from the thermo-on operation to the thermo-off operation and in a case where there is none of the indoor units is in the thermo-on operation other than the indoor unit A, there can be made an air conditioning apparatus that can suppress an increase in power consumption associated with start-stop of the compressor by reducing the start-stop frequency of the compressor and is high in energy saving property.

In the following, the air conditioning apparatus of the present invention will be described in detail by using FIG. 1 to FIG. 12.

First Embodiment

A first embodiment of the present invention will be described by using FIG. 1 to FIG. 8.

FIG. 1 is a cycle system diagram showing a configuration of an air conditioning apparatus in the present embodiment. In the present embodiment, an example that two indoor units (91 a, 91 b) have been connected to one outdoor unit 90 is shown. The present invention is not limited to this and both of the outdoor unit 90, the indoor unit 91 may be different in number of connected units.

The two indoor units (91 a, 91 b) are connected in parallel with the outdoor unit 90 via a liquid pipe 13 and a gas pipe 12. The outdoor unit 90 possesses therein a compressor 1 that compresses a refrigerant (not shown), an outdoor heat exchanger 3 that performs heat exchange between outdoor air supplied by an outdoor fan 4 and the refrigerant, a four-way valve 5 for switchingly connecting one of a suction port and a discharge port of the compressor 1 to the outdoor heat exchanger 3 and the other to the gas pipe 12. The other end of the outdoor heat exchanger 3 to be connected with the four-way valve 5 is connected to the liquid pipe 13 via an outdoor expansion valve 8.

In the indoor unit 91, one of an indoor heat exchanger 16 is connected to the gas pipe 12 and the other is connected to the liquid pipe 13 via an indoor expansion valve 18. Suction air from an indoor space is supplied to the indoor heat exchanger 16 by an indoor fan 17. A user performs operation start and stop of the indoor units, designation of operation modes for cooling and heating, inputting of a set temperature and so forth by a remote controller 92. The air conditioning capability of the air conditioning apparatus is determined on the basis of a temperature difference between the set temperature and a sensed temperature (a suction temperature) of a suction air temperature sensor 21.

As shown in FIG. 2, when an operation start signal is input into a controller 60 from the remote controller 92, the operation of the air conditioning apparatus is started and a control signal is sent from the controller 60 to each of actuators of the outdoor unit 90 and the indoor units 91.

An operation will be described with regard to a case where there is a request for a cooling operation from a remote controller 92 a. In this case, in FIG. 1, a four-way valve 2 is switched to a circuit shown by a solid line in the drawing to operate the outdoor fan 4 and an indoor fan 17 a at predetermined rotation frequencies.

The refrigerant that has been compressed by the compressor 1 is condensed and liquefied by being heat-exchanged with the outdoor air by the outdoor heat exchanger 3. The liquefied refrigerant that has flown out into the liquid pipe 13 via the outdoor expansion valve 8 that is in a fully open state is pressure-reduced by an indoor expansion valve 18 a to be low in temperature and low in pressure and flows into the indoor heat exchanger 16. The refrigerant that has absorbed heat from the indoor air evaporates and turns to an overheated gaseous refrigerant and flows out into the gas pipe 12. The indoor air that has been cooled by this action is supplied to the indoor space and cools the indoor space. The gasified refrigerant passes through the gas pipe 12 and returns to the compressor 1 via the four-way valve 2 in the outdoor unit 90. At this time, an indoor expansion valve 18 b is in a fully closed state and an indoor fan 17 b is in a stopped state.

In a case where there is an operation start signal also from a remote controller 92 b, also the indoor expansion valve 18 b is appropriately adjusted in opening, the refrigerant in the liquid pipe 13 is pressure-reduced and flows into an indoor heat exchanger 16 b and is subjected to heat exchange with the indoor air that has been supplied by the indoor fan 17 b. The evaporated gaseous refrigerant joins with the refrigerant that has evaporated in the indoor unit 92 a and returns to the outdoor unit 90.

On the other hand, in a case where there are requests for the heating operation from the remote controllers 92 a and 92 b, the four-way valve is switched to a circuit shown by a broken line in FIG. 1 to operate the outdoor fan 4 and the indoor fan 17 at the predetermined rotation frequencies. The refrigerant that has been compressed by the compressor 1 flows into the indoor heat exchangers 16 a, 16 b through the gas pipe 12. In the indoor heat exchanger 16, the refrigerant is condensed and liquefied and on the other hand the indoor space is heated by radiating heat to the indoor air supplied by the indoor fan 17. After joined in the liquid pipe 13, the condensed liquefied refrigerant turns to the low-temperature/low-pressure refrigerant by being pressure-reduced by the outdoor expansion valve 8 and evaporates by receiving heat from the outdoor air by the outdoor heat exchanger 3. Thereafter, it returns to the compressor 1 via the four-way valve 2 and repeats again a compression process.

An operation at the time of cooling in such an air conditioning apparatus will be described in detail. The rotation frequency of the compressor 1 is controlled such that a suction air temperature Tin1 that a suction thermistor 21 of each indoor unit 91 has sensed becomes equal to a set temperature Ts set by the remote controller. However, in a case where the capability of the air conditioning apparatus is excessive relative to an indoor load, in a case where the indoor load is smaller than the capability of the air conditioning apparatus when operated by a lower limit capability of the compressor 1 and so forth, in some cases the suction air temperature Tin of the indoor unit 91 becomes lower than the set temperature.

In such a case, the thermo-off operation that the indoor expansion valve 18 of the indoor unit 91 is closed to suspend the cooling operation is performed. Since in the thermo-off operation, the refrigerant is no longer supplied to the indoor heat exchanger 16, a cooling action by evaporation of the refrigerant ceases. Accordingly, the room temperature is gradually increased by the load of the indoor space. Then, when the suction temperature is increased up to a predetermined temperature, the indoor expansion valve 18 is again opened to restart the thermo-on operation.

FIG. 3 is a diagram schematically showing the operation of such conventional control. The horizontal axis indicates a time, the vertical axis indicates room temperatures (that is, the suction air temperature Tin) of the indoor units 91 a and 91 b, states of the thermo-on operation and the thermo-off operation and the operation state of the compressor.

The indoor unit 91 enters the thermo-on operation at a point of time that the suction air temperature Tin has reached a thermo-on lower limit value LL and thereafter enters the thermo-on operation at a point of time that the temperature has reached a thermo-off upper limit value HL. Here, a case where HL1 is +2° C. and LL is −1° C. relative to the set temperature and a temperature width is 3° C. is shown. Incidentally, the present embodiment is one example with respect to the widths of HL and LL relative to the set temperature and the condition when making it thermo-on or thermo-off, and conditions such as the time and others may be added not limited to the suction air temperature Tin.

In FIG. 3, although both of the two indoor units 91 operate at the start time, since the suction air temperature Tin1 of the indoor unit 91 a has reached a lower limit value LL1 at a time t1, the indoor unit 91 a enters the thermo-off operation. Thereafter, the indoor unit 91 b continues the operation alone, and at a point of time that it has reached a lower limit value LL2 at a time t2, also the indoor unit 91 b enters the thermo-off operation.

In this occasion, since both of the indoor units 91 a, 91 b have entered the thermo-off operation, also the compressor 1 enters the stop state. When the times at which the plurality of indoor units 91 a, 91 b enter the thermo-off operation accidentally coincide with each other in this way, the necessity to stop the compressor 1 arises. When the compressor 1 enters the stop state, such an energy loss that a high-temperature refrigerant and a low-temperature refrigerant are mixed together occurs and therefore the power consumption is more increased than in the operation with no stop.

In addition, when once the compressor 1 enters the stop state, pressure equalization at an inlet and an outlet of the compressor 1 becomes necessary and therefore it cannot be restarted for about three minutes in general. Accordingly, although the room temperature of the indoor unit 91 a exceeds a thermo-off upper limit value HL1 at a time t3, it cannot be made thermo-on until a time t4 that start of the compressor 1 becomes possible comes.

Like this, in the conventional control, there is the possibility that the room temperature may be increased while the compressor 1 is stopping and there was a problem also in terms of comfort.

Accordingly, in the present embodiment, means for temporarily changing a condition that the indoor unit was made thermo-off in a case where all of the indoor units met the condition for entering the thermo-off operation was provided. An operational example in this case is shown in FIG. 4 and a flowchart of this control is shown in FIG. 5.

The point that after the indoor unit 91 a has entered the thermo-off operation at the time t1, the indoor unit 91 b continues the operation alone is the same as the conventional control. Thereafter, at a point of time that a suction air temperature Tin2 (that is, the room temperature) that the suction thermistor 21 of the indoor unit 91 b has sensed has reached a thermo-on lower limit value LL2, the control of the present invention is performed. That is, when it is sensed that when the indoor unit 91 b is stopped, all of the indoor units (91 a, 91 b) enter the thermo-off operation in the controller 60, it shifts to the start-stop suppression operation mode without making the indoor unit 91 b perform the thermo-off operation. Then, it lowers the thermo-on lower limit value LL2 by a predetermined temperature (for example, 1° C.) and sends a command to the indoor unit 91 b so as to continue the thermo-on operation. Thereby, the state that the indoor unit 91 b is immediately made thermo-off can be avoided and it can wait until the other indoor unit (91 a, in the present embodiment) is made thermo-on. Accordingly, since start-stop of the compressor 1 can be suppressed, an increase in compression power is avoided and the energy saving property can be increased.

Then, at a point of time that the indoor unit 91 a has been made thermo-on, the start-stop suppression operation mode is terminated to return the thermo-on lower limit value LL2 to the normal value. Thereby, the indoor unit 91 b shifts to the thermo-off operation.

Since the thermo-off lower limit value LL is returned to the original value after termination of the present control in this way, after termination of the present control, the operation within a normal temperature range is continued. Accordingly, reduction in temperature is limited to the temporal one and such an inconvenience that the room temperature stays low and so forth does not occur and the comfort can be maintained.

Incidentally, during the start-stop suppression operation mode, the suction air temperature Tin2 of the indoor unit 91 b is temporarily lowered. Thus, in the present embodiment, it was made such that while the operation of the indoor unit 91 b is continued, the thermo-off upper limit value HL2 that the indoor unit 91 a that is in the thermo-off operation is made thermo-on is lowered by a predetermined width (for example, 1° C.). Accordingly, shifting to the thermo-on operation becomes possible even in a state that the temperature difference between it and the set temperature is small.

Thereby, although, at a time t3, the suction air temperature Tin1 of the indoor unit 91 a does not reach the temperature that it normally shifts to the thermo-on operation, it becomes possible to shift it to the thermo-on operation early. Since it became possible to shift the indoor unit 91 a that had been in the thermo-off operation so far to the thermo-on operation, the present control is terminated at this point of time, thereby returning from the start-stop suppression operation mode to a normal operation mode. That is, control of lowering the thermo-off upper limit value HL1 and the thermo-on lower limit value LL2 is released to return it to the normal state. Therefore, the indoor unit 91 b enters the thermo-off operation. Since a reduction width of the suction air temperature Tin2 of the indoor unit 91 b can be suppressed by the present control in this way, the power consumption of the air conditioning apparatus can be reduced while reducing the influence on the comfort.

As described above, since the present control works when it is decided that all of the indoor units 91 will enter the thermo-off operation, it becomes possible to surely avoid stop of the compressor 1 when needed. Accordingly, an effect of always suppressing start-stop can be obtained not depending on cyclicity and so forth that the plurality of indoor units repeat thermo-on/thermo-off.

Incidentally, although in the present embodiment, it was made such that the start-stop suppression operation mode is terminated at the point of time that the indoor unit 91 a has been made thermo-off, operating times of the indoor units 91 a and 91 b may be overlapped for a predetermined time in order to suppress a fluctuation in refrigerating cycle at a timing of switching.

In addition, although in the present embodiment, it was made such that the temperature of the threshold value is changed in order to extend the thermo-on operation time of the indoor unit 91 b, means for extending the thermo-on operation time of the indoor unit 91 b may be other means. Specifically, it may be a technique for extending a time for deciding to be thermo-off after having reached the threshold temperature. In addition, it may be a technique for making it perform an air conditioning operation that is the same as that for thermo-off by forcedly adjusting the opening of the indoor expansion valve 18 from the outdoor unit and so forth, in a case where the indoor unit has been decided to be thermo-off.

In addition, although in the present embodiment, the example has been described that when the thermo-off condition for the indoor unit 91 b has been met, it enters the start-stop suppression operation mode, it may be made such that, for example, in a case where the plurality of indoor units are connected, the possibility of continuation of the operation by the start-stop suppression operation mode is set in advance for every indoor unit. Accordingly, although in a case where continuation of the operation by the start-stop suppression operation mode has been set to be possible, it operates as in the present embodiment, for example, in a case where continuation of the thermo-on operation by the start-stop suppression operation mode has been set to be impossible for the indoor unit 91 b, it may be set so as to stop it similarly to FIG. 3. In this case, since in a case where all of the indoor units 91 have met the condition to be made thermo-off, there arise a case where the compressor 1 is stopped and a case where it continues the operation depending on the indoor unit that has finally continued the operation, also a condition that an increase in power consumption associated with start-stop of the compressor 1 cannot be avoided arises. However, it is possible to possess a function of giving priority to the comfort on the user side in accordance with the installation situation and so forth of the indoor units 91.

An operation at the time of heating operation is shown in FIG. 6. Also at the time of heating similarly to the time of cooling, the indoor unit 91 a enters the thermo-off operation at the time t1 that it has reached the thermo-on upper limit temperature HL1. Thereafter, although the suction air temperature Tin2 of the indoor unit 91 b keeps increasing and reaches the thermo-on upper limit temperature HL2 at the time t2, since all of the indoor units 91 enter the thermo-off operation when the indoor unit 91 b is made thermo-off, the thermo-on upper limit temperature of the thermo-on indoor unit 91 b is set high by a predetermined temperature. Thereby, the indoor unit 91 b can continue the thermo-on operation. Further, since the thermo-off lower limit value of the thermo-off indoor unit 91 a is set high by a predetermined value, it is possible to make the indoor unit 91 a thermo-on early and as a result the indoor unit 91 b can be made thermo-off. Accordingly, an increase in suction air temperature Tin2 in the indoor unit 91 b can be suppressed.

There can be provided the air conditioning apparatus that, also in the heating operation, can suppress an increase in power consumption by avoiding start-stop of the compressor 1 while maintaining the comfort and is high in energy saving property in this way.

FIG. 7 shows an operational example in a case where air conditioning loads are different. Since all of the indoor units 91 meet the thermo-off condition at the time t2, it enters the start-stop suppression operation mode also in the present embodiment. Then, while the thermo-on lower limit temperature LL2 of the thermo-on indoor unit 91 b is lowered, the thermo-off upper limit temperature HL1 of the indoor unit 91 a is lowered.

When the operation is continued under this condition, since the suction air temperature Tin2 of the indoor unit 91 b keeps lowering, in a case where a time is required until the indoor unit 91 a is made thermo-on, the problem becomes big in terms of the comfort. In addition, also the evaporating temperature of the refrigerating cycle is lowered with lowering the suction air temperature Tin2 of the indoor unit 91 b, the efficiency of the refrigerating cycle is also lowered and the power consumption is increased. Accordingly, there is the possibility that the effect of power consumption suppression brought about by suppressing start-stop of the compressor 1 cannot be sufficiently obtained.

Therefore, in the present embodiment, it was made such that the start-stop suppression operation mode is terminated at a point of time that the value of the suction air temperature Tin2 of the indoor unit 91 b has reached the corrected thermo-on lower limit value LL2. Therefore, not only unnecessary continuation of the operation that is poor in efficiency can be avoided, but also reduction in comfort can be prevented.

FIG. 8 is an example that a limit has been set on a duration time of the start-stop suppression operation mode, not setting the lower limit value of the suction air temperature Tin2 of the indoor unit 91 b for the similar problem. A timer is counted from a point of time that it has shifted to the start-stop suppression operation mode at the time t2, in a case where the indoor unit 91 a cannot be made thermo-on at the time t3 that it has elapsed for a time limit ΔT that has been defined in advance, it is decided that the load on the indoor unit 91 a is small and further continuation of the operation of the indoor unit 91 b is low in energy saving effect, the present control is released, the thermo-off upper limit value HL1 of the indoor unit 91 a and the thermo-on lower limit value LL2 of the indoor unit 91 b are returned to their original values and the indoor unit 91 b is made thermo-off to put the compressor 1 into the stop state.

Accordingly, since the operation of the compressor 1 in a state that the refrigerating cycle efficiency is poor can be restricted, an increase in unnecessary power consumption can be avoided. The present control is effective particularly in a case where the thermo-off operation time is long.

Second Embodiment

Next, a control operation in a case where decision of start of the start-stop suppression operation mode is to be made will be described. FIG. 9 is a flowchart of the present control.

In the flowchart in FIG. 9, for the first embodiment, the step of deciding whether an indoor unit that is in a thermo-on standby state is present has been added before starting the start-stop suppression operation mode. The thermo-on standby state indicates a state that the suction air temperature Tin is higher (lower in the case of heating) than a previously defined predetermined temperature, the presence/absence of the indoor unit that is liable to be thermo-on is decided and start of the start-stop suppression operation mode is decided on the basis of it.

An operational example of the present control will be described by using FIG. 10. Also in the present embodiment, the indoor unit 91 a enters the thermo-off operation at the time t1 and also the indoor unit 91 b meets the thermo-off condition at the time t2. In such a case, for example, in the operational example shown in FIG. 7 of the first embodiment, although it was made such that the indoor unit 91 b is maintained in the thermo-on operation up to the time limit, in the present embodiment, whether the start-stop suppression operation mode is to be started is decided by confirming the state of the thermo-off indoor unit 91 a.

In the first embodiment, the operational example that the lower limit values of the time limit and the room temperature are set so as to minimize an increase in power consumption and reduction in comfort caused by the start-stop suppression operation mode was shown. In the present embodiment, whether the indoor unit 91 a will shift to the thermo-on operation in a predetermined time is estimated, in a case where it is decided that the indoor unit 91 a will enter the thermo-on operation early, the indoor unit 91 b is maintained in the thermo-on operation by shifting to the start-stop suppression operation mode. On the other hand, in a case where it has been decided that a time will be required until the indoor unit 91 a enters the thermo-on operation, the indoor unit 91 b is shifted to the thermo-off operation not shifting to the start-stop suppression operation mode.

In the present embodiment, in order to decide whether the thermo-off indoor unit 91 a will enter the thermo-on operation early, decision is made by using the suction air temperature Tin1 of the indoor unit 91 a. That is, a decision temperature TC1 that is higher than the thermo-on lower limit value LL1 and not more than the thermo-off upper limit value HL1 is defined and whether the thermo-off indoor unit will enter the thermo-on operation early is decided by using this decision temperature TC1. More specifically, in a case where the suction air temperature Tin1 of the thermo-off indoor unit 91 a is at least TC1, it is decided that it is in the thermo-on standby state that the possibility that it will be made thermo-on early is high, and the thermo-on operation of the indoor unit 91 b is continued only in a case where there exists the indoor unit that is in the thermo-on standby state.

In the present embodiment, since the suction air temperature Tin1 of the thermo-off indoor unit 91 a is lower than the decision temperature TC1 at the time t2 and there exists none of the indoor units is in the thermo-on standby state, the indoor unit 91 b is stopped at the time t2. Accordingly, at the time t3 that the suction air temperature Tin2 of the indoor unit 91 b has reached the thermo-off upper limit temperature HL2 after the compressor 1 has been stopped similarly to the normal control, the compressor 1 is restarted. Under a condition that when shifting to the start-stop suppression operation mode, the suction air temperature Tin2 of the indoor unit 91 b is lowered and the efficiency of the refrigerating cycle is reduced in this way, the compressor 1 is once stopped positively so as to avoid these problems. That is, since an operation method that is to be assumed to be little in power consumption can be selected for a case where start-stop of the compressor is suppressed by using the start-stop suppression operation mode and a case where the compressor has been once stopped without using the start-stop suppression operation mode, there can be finally provided the air conditioning apparatus that is high in energy saving property.

Incidentally, in the present embodiment, it was made such that decision of start of the start-stop suppression operation mode is made when it is decided that the indoor units that perform the thermo-on operation will drop to zero. For example, in a case where it was made to start it when one indoor unit performs the operation alone, since the suction air temperature of the indoor unit concerned is still high and a time is required until the thermo-off condition is met, it is difficult to estimate the suction air temperatures and so forth of other indoor units at a point of time that the thermo-off condition is met, such a decision cannot be made. In the present embodiment, when it is decided that the indoor units that perform the thermo-on operation will drop to zero, start of the start-stop suppression operation mode can be decided by using information on other indoor units at that time.

Incidentally, although in the present embodiment, it was made such that decision is made on the basis of whether there exists the indoor unit that is in the thermo-on standby state in order to decide start of the start-stop suppression operation mode, the present invention is not limited to that and decision may be made by using, for example, a time that the suction air temperature of the indoor unit is changed, a thermo-off time in the past operation and so forth. In the present invention, since it was made such that start of the start-stop suppression operation mode is decided when it is decided that the thermo-on indoor units will drop to zero, decision can be made by using the information on other indoor units at that time.

Third Embodiment

An embodiment in a case where the thermo-on lower limit values have been set in two stages is shown in FIG. 11. Since when the thermo-on lower limit value LL is lowered, the room temperature is temporarily lowered, in the present embodiment, in order to prevent this, a second thermo-on lower limit value mL was set to a temperature that is higher than the normal thermo-on lower limit value LL. Normally, it is made thermo-off at a point of time that the temperature has been lowered down to mL and the threshold value for thermo-off is lowered down to LL only when it has entered the start-stop suppression operation mode.

An operational example will be described by using FIG. 11. Since the suction temperature Tin1 of the indoor unit 91 a has reached mL1 at the time t1, the indoor unit 91 a is brought into the thermo-off state. Thereafter, since the suction temperature Tin2 of the indoor unit 91 b keeps lowering and reaches mL2 at the time t2, the indoor unit 91 b meets the thermo-off condition. However, at this time, when the indoor unit 91 b is made thermo-off, since the thermo-on indoor unit is lost and the compressor should be stopped, it shifts to the start-stop suppression operation mode. Thereby, the thermo-on lower limit value of the indoor unit 91 b is changed from mL2 to LL2 to continue the cooling operation of the indoor unit 91 b. Thereafter, when the indoor unit 91 a is made thermo-on associated with an increase in temperature, the start-stop suppression operation mode is terminated and the indoor unit 91 b is shifted to the thermo-off state.

At this time, although the suction temperature of the indoor unit 91 b is more lowered than mL2, it is not lowered down to LL2. Accordingly, an increase in power consumption associated with stop and start of the compressor can be suppressed by lowering a blow-out temperature of the indoor unit 91 b without giving the user an unpleasant feeling.

Fourth Embodiment

FIG. 12 is a diagram showing an operational example in a case where an indoor unit that is to be made thermo-on in the start-stop suppression operation mode has been fixed. In the present embodiment, a case where three indoor units have been connected in parallel with one another is shown by way of example. In the present embodiment, in order to prevent all of the indoor units from being made thermo-off, it is set in advance such that an indoor unit 91 c is made thermo-on in a case where all of the indoor units are to be made thermo-off.

In the present embodiment, since the suction temperature Tint of the indoor unit 91 a and the suction temperature Tin2 of the indoor unit 91 b have respectively reached the thermo-on lower limit value LL at the time t1 and the time t2, they meet the thermo-off condition. Since the indoor unit 91 c is in the thermo-off state, when the indoor unit 91 b is made thermo-off at the time t2, all of the indoor units enter the thermo-off states and the compressor 1 is stopped. Thus, in the present embodiment, the indoor unit 91 c is shifted to the thermo-on state by working the start-stop suppression operation mode so as to avoid stop of the compressor 1. Then, at the time t3 that the indoor unit 91 a has entered the thermo-on state, the indoor unit 91 c is returned to the thermo-off state. Although the indoor unit 91 c may be left in the thermo-on state, the operating time in a state that the suction temperature of the indoor unit 91 c is in a low state is increased in this case and therefore it is desirable to bring it to the thermo-off state. In particular, under such a condition that the start-stop suppression operation mode frequently occurs, since there is the possibility that the state that the suction temperature of the indoor unit 91 c is low may last, it becomes easy to avoid such a condition by returning it to the thermo-off state.

Lowering of the suction temperatures in the indoor units 91 a and 91 b can be prevented by fixing the indoor unit that enters the thermo-on state in the start-stop suppression operation mode in this way. Accordingly, in a case where the indoor units 91 a and 91 b are installed in a place (such as a small room and so forth) where it is wished to avoid reduction in suction temperature, lowering and excessive rising of room temperature by such indoor units can be avoided. In addition, an increase in power consumption associated with start-stop of the compressor can be suppressed while suppressing the unpleasant feeling given to the user by selecting the indoor units and so forth that are little in influence that a change in suction temperature per unit gives to the user such as the indoor units and so forth that are installed in the large space.

LIST OF REFERENCE SIGNS

-   60 . . . controller -   91 a, 91 b . . . indoor unit 

1. An air conditioning apparatus, comprising: a refrigeration cycle device formed by connecting an outdoor unit equipped with a compressor with a plurality of indoor units, the indoor unit performing an air conditioning operation by switching between an thermo-on operation for performing a cooling operation or a heating operation and a thermo-off operation for suspending the cooling operation or the heating operation by using information on temperature difference between a suction air temperature and a set temperature, wherein in a case where a first indoor unit in the indoor units has met a thermo-off condition for switching from the thermo-on operation to the thermo-off operation and in a case where none of the indoor units is in the thermo-on operation other than the first indoor unit, the first indoor unit shifts to a start-stop suppression operation mode for making one of the indoor units perform the thermo-on operation.
 2. The air conditioning apparatus according to claim 1, wherein in a case where the first indoor unit in the indoor units has met the thermo-off condition for switching from the thermo-on operation to the thermo-off operation and in a case where none of the indoor units is in the thermo-on operation other than the first indoor unit, the first indoor unit shifts to the start-stop suppression operation mode for making the indoor unit that has been designated in advance in the indoor units perform the thermo-on operation.
 3. The air conditioning apparatus according to claim 1, wherein in a case where the first indoor unit in the indoor units has met the thermo-off condition for switching from the thermo-on operation to the thermo-off operation and in a case where none of the indoor units is in the thermo-on operation other than the first indoor unit, the first indoor unit shifts to the start-stop suppression operation mode to continue the thermo-on operation without switching the first indoor unit to the thermo-off operation.
 4. The air conditioning apparatus according to claim 3, wherein even in a case where the first indoor unit has met the thermo-off condition for switching from the thermo-on operation to the thermo-off operation and in a case where none of the indoor units is in the thermo-on operation other than the first indoor unit, in a case where it has been decided that the second indoor unit that is the indoor unit other than the first indoor unit does not shift to the thermo-on operation in a predetermined time, the first indoor unit is not shifted to the start-stop suppression operation mode.
 5. The air conditioning apparatus according to claim 4, wherein in a case where a difference between the suction air temperature of the second indoor unit and a thermo-on temperature at which the second indoor unit is switched to the thermo-on operation is within a predetermined value, it is decided that the second indoor unit will shift to the thermo-on operation in the predetermined time, and in a case where the difference between the suction air temperature of the second indoor unit and the thermo-on temperature at which the second indoor unit is switched to the thermo-on operation is at least the predetermined value, it is decided that the second indoor unit will not shift to the thermo-on operation in the predetermined time.
 6. The air conditioning apparatus according to claim 3, wherein only in a case where the indoor unit of which shifting to the start-stop suppression mode is allowed is designated in advance and the first indoor unit is the indoor unit of which shifting to the start-stop suppression mode has been allowed, it is shifted to the start-stop suppression operation mode.
 7. The air conditioning apparatus according to claim 3, wherein in the start-stop suppression mode, the thermo-off temperature at which the first indoor unit is made thermo-off is changed to a first thermo-off temperature that has been increased in difference between the thermo-off temperature and the set temperature.
 8. The air conditioning apparatus according to claim 7, wherein the start-stop suppression operation mode is terminated at a point of time that the suction temperature of the first indoor unit has reached the first thermo-off temperature.
 9. The air conditioning apparatus according to claim 3, wherein the start-stop suppression operation mode is terminated at a point of time that any one of the indoor units other than the first indoor unit switches to the thermo-on operation.
 10. The air conditioning apparatus according to claim 1, wherein the start-stop suppression operation mode is terminated at a point of time that a predetermined time has elapsed after shifted to the start-stop suppression operation mode.
 11. The air conditioning apparatus according to claim 1, wherein in the start-stop suppression operation mode, the thermo-on temperature at which the indoor unit other than the first indoor unit is made thermo-on is changed to the first thermo-on temperature that has been reduced in difference between the thermo-on temperature and the set temperature. 